How to correct photo time using a GPS

A few years back when I got my GPS, I was very happy to be able to geotag my photos. However, I didn’t realize how much my camera time was desynchronising until I noticed that some pictures were not correctly mapped at all because the camera was losing a few minutes every week.

After that, I was setting the camera time when I was going out, except when I forgot, which happened almost every time. And since I became an active member on OpenStreetMap, I started taking pictures of every useful object I could find on my way, I had to find other options to keep my photos up to date in order to map them correctly.

GPS time

I quickly realised that the easiest way would be to take a picture of the time in order to correct it. Based on this photo, I can correct the time of all the photos of my shooting session because it contains an image of the correct time from the GPS and the camera metadata that include the camera time, which is retrievable using exiftool or exiv2 on a UNIX system, or many other tools on Windows and Mac (ViewNX2, GPSPhotoLinker, etc.). Here’s the command line to get the data from exiftool:

exiftool -s -SubSecDateTimeOriginal DSC_9117.JPG 
SubSecDateTimeOriginal : 2013:02:16 21:25:47.80

Based on that, we can see a difference of 41 seconds between the metadata and the GPS time (precision is about more or less one second), where the camera is in advance.

We can now correct the picture time, using exiv2:

exiv2 -a -00:00:41 DSC_9117.JPG 
exiftool -s -SubSecDateTimeOriginal DSC_9117.JPG 
SubSecDateTimeOriginal : 2013:02:16 21:25:06.80

Time is now matching the GPS time, so I can apply the exiv2 command to the other photos.

Note: I use the UTC time zone in both my camera and GPS so I don’t have to worry or set local time on both devices. If the time zones are different, some additional correction may be wanted.

During my last holiday, some people saw me correcting the time of my photos by 8 seconds and really thought I was a nerd because it would make not much difference, but I like it when it’s precise 😉

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Things to take care when buying a used Lens

Ever considered buying some second hand camera lens? twiching.com has written a post for the non expert.

Know what you’re after. Do a bit of research on the lens you want. Classifieds, eBay, etc will give you an idea of the price, and camera forums will give you an idea of common problems to check for with specific models. Both of those are probably more useful than most of the stuff below.

With that in mind, here’s some general steps for checking out a lens…

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Error’d: Luck of the Draw

"One of these icons closes the current window, one completely exits the program," observed Sam Oldak.

 

"Anna asked me if she was helpful and I tried to be honest," wrote Virginia, "Part of the problem could be she doesn't understand the most important word in the English language."

 

"I spotted this amazing offer in WH Smith a while back. I decided not to go for it though," wrote Colin Cameron.

 

"Not only do they not have technology to add spaces to their error messages," writes Aiden, "the monospace messages don't even fit in the div properly."

 

Daniel apparently likes to plan things well in advance.

 

Jack Botner received this less-than-stellar offer after purchasing an item on eBay.

 

"I thought I was just saving a nine page PDF, but I must've miscounted. Apparently the real number was 18,446,744,073,709,600,000," wrote Brett.

 

Steve Jones wrote, "The box it came in definitely implied that printing was a supported feature."

 

Huge natural gas producer severs Website, email after malware attack

A liquefied natural gas plant in operation.

One of the world’s biggest producers of liquefied natural gas has been hit by a malware attack that has taken down its website and e-mail servers. This is the second documented computer attack to hit a large energy company this month.

Officials with Qatar-based RasGas first identified an “unknown virus” on Monday and took their RasGas.com website and e-mail servers offline in response, Bloomberg News and other news agencies reported on Thursday morning, citing company representatives. Operational systems weren’t affected and production and deliveries remain intact. A joint venture between Qatar Petroleum and ExxonMobil, RasGas exports about 36.3 million tons of liquefied natural gas per year.

News of the attack comes four days after Saudi Aramco, the world’s largest oil producer, confirmed it was the victim of a separate malware attack that took down 30,000 workstations. The assault against the Saudi Arabia-based company was launched on August 15 as the malware entered through its network of personal computers. Oil production wasn’t affected, company officials have said.

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